Modelling of infectious spreading in heterogeneous polymer oxidation I. Development of a stochastic model

Abstract

The heterogeneous features of the oxidation of polypropylene in the amorphous region are consistent with infectious spreading from a small number of sites, such as catalyst residues. A stochastic model was developed for demonstrating the spatial and temporal development of oxidation from these sites. In this model, the probability of passing the infection from one site to an adjacent site could be used in place of conventional rate constants. The probability of spreading was assumed to be temperature dependent, and modelled with Arrhenius behaviour. Each site was given a predefined lifetime such that the maximum probability of spreading coincided with the maximum rate of oxidation at a particular site. This has enabled visualisation of the spatial development of oxidation within the amorphous region. The epidemiological fractions corresponding to the remaining (unoxidised) polymer, the dead (oxidised) polymer and the infectious (oxidising) polymer, were calculated and used to test the limitations of the simple epidemiological model.